Phase Change and Density Warm up question: How does a substances density change when changing to a different state of matter?

What do you think? In your notebook write a hypothesis (if, then, because) for the following problem: – What happens to density as phase changes from gas to liquid to solid? Compare your hypothesis with your partner. Are they the same or different? Whose do you think is correct?

Density and Phase Change Remember that density is the MASS of matter divided by the VOLUME! – D = m/v Which do you think takes up more space 100g of water or 100g of water vapor? – 100g of water vapor – Remember that gases have their molecules more “spread” out and therefore takes up more space!

Calculate the density of water and water vapor 100g of water has a volume of 100 mL…What is the density? – D=m/v – D = 100g/100mL – D = 1g/mL 100g of water vapor has a volume of 120mL…What is the density? – D= 100g/120mL – D= 0.83 g/mL Liquid has the higher density!

Liquid to Solid Phase Change What do you think happens to density as a liquid changes to a solid? Why? Which takes up more space 100g of liquid gold or 100g of solid gold? Why do you think this? – Remember: In a solid the molecules are more compact (takes up less space)

Calculate 100g of liquid gold has a volume of 6.5mL. – D=m/v – D=100g/6.5mL – D=15.4g/mL 100g of solid gold has a volume of 5.2mL – D=100g/5.2mL – D=19.3g/mL

In General…. In general what happens to density as we go from solid to liquid to gas? – As we go from solid to liquid to gas, density generally decreases (this is why gas floats on liquid and liquid floats on solid)

EXCEPTION What happens to water as it is frozen? – Why does ice float on water, why do soda cans crack in the freezer? – As water freezes it expands, making ice (solid) less dense than the liquid form! Phase change demo

LAB SAFETY AND YOU A STUDENT GUIDE Today’s Topic: MSDS Sheets T. Givens / Mister Science 2013 / All Rights Reserved

WE communicate Safety in many ways… Can you guess where you might see each picture? T. Givens / Mister Science 2013 / All Rights Reserved

WHY might we need more in- depth safety information? The Signs you just saw communicated safety information with just a picture and perhaps a few simple words. Think about the following question for 30 seconds. Why might we need more in-depth safety information? After thinking quietly, pair with a neighbor and share your thoughts. T. Givens / Mister Science 2013 / All Rights Reserved

What is an MSDS? MSDS stands for “Material Safety Data Sheet”. It is intended to provide workers and emergency personnel with procedures for handling or working with substances in a safe manner, and includes information such as physical data (melting point, boiling point, flash point, etc.), toxicity, health effects, first aid, reactivity, storage, disposal, protective equipment, and spill-handling procedures. MSDS formats can vary from source to source within a country depending on national requirements. T. Givens / Mister Science 2013 / All Rights Reserved

Have you ever seen these symbols? T. Givens / Mister Science 2013 / All Rights Reserved

Examples of Chemicals requiring an MSDS ChemicalHealthFireReactivity Fluorine403 Sulfuric Acid301 Carbon Monoxide 240 Chloroform200 T. Givens / Mister Science 2013 / All Rights Reserved

Fluorine Fluorine gas is the most reactive of all the elements and quickly attacks all metals - steel wool bursts into flames when exposed to it ! In very small amounts, it is also a trace element necessary for the health of most organisms. The element and various compounds have a number of uses, ranging from the construction of nuclear bombs to additives in dental products which are designed to promote oral health. T. Givens / Mister Science 2013 / All Rights Reserved

Sulfuric Acid Sulfuric acid is one of the most important industrial chemicals. More of it is made each year than is made of any other manufactured chemical; It has widely varied uses and plays some part in the production of nearly all manufactured goods. The major use of sulfuric acid is in the production of fertilizers. It is widely used in the manufacture of chemicals, e.g., in making hydrochloric acid, nitric acid, sulfate salts, synthetic detergents, dyes and pigments, explosives, and drugs. It is used in petroleum refining to wash impurities out of gasoline and other refinery products. Sulfuric acid is used in processing metals, e.g., in pickling (cleaning) iron and steel before plating them with tin or zinc. Rayon is made with sulfuric acid. T. Givens / Mister Science 2013 / All Rights Reserved