Taking Mass and Volume Measurements with Accuracy & Precision

What is a measurement? Measurement is the process of determining a physical quantity such as length, time, temperature, etc.

Accuracy & Precision Accuracy: how close a measured value is to the actual (true) value. Accuracy: how close a measured value is to the actual (true) value. For example: The actual density of gold is g/cm 3. If you measure the density of gold and your value is fairly close to g/cm 3, then you took an accurate measurement. For example: The actual density of gold is g/cm 3. If you measure the density of gold and your value is fairly close to g/cm 3, then you took an accurate measurement.

Accuracy & Precision Precision is consistently getting the same measurement even if it is not right. Precision is consistently getting the same measurement even if it is not right.

Accuracy vs. Precision Low Accuracy High AccuracyHigh Accuracy High Precision Low Precision High Precision

Why Does This Matter? It is important to take accurate and precision measurements because we will be using many chemicals this term like: CaO 2, AgNO 3, NaOH, HCl, H 2 O 2,, and more. It is important to take accurate and precision measurements because we will be using many chemicals this term like: CaO 2, AgNO 3, NaOH, HCl, H 2 O 2,, and more. Mixing too much of a substance can potentially create a violent reaction. Mixing too much of a substance can potentially create a violent reaction. 2Q&feature=related 2Q&feature=related NE&feature=fvwrel NE&feature=fvwrel

Today’s Measuring Focus: Mass Mass Volume Volume Density Density

What is Mass Mass is the amount of matter in a substance… it is NOT weight. Mass is the amount of matter in a substance… it is NOT weight. However, you can find an object’s weight by multiplying its mass by the acceleration of gravity which is… However, you can find an object’s weight by multiplying its mass by the acceleration of gravity which is… 9.8 m/s 2

Mass is measured with a… Triple Beam Balance or… Triple Beam Balance or… Electronic Scale Electronic Scale

Units for Mass The triple beam balance gives mass in grams (g) The triple beam balance gives mass in grams (g) But there are many other units for mass like: But there are many other units for mass like: Kilograms (kg) Kilograms (kg) Milligrams (mg) Milligrams (mg) 1 kg = 1000 g1 g = 1000 mg

Total Mass = g ….or kg 70 g 300 g 3.4 g

Your Turn Find the mass of the object given to you Find the mass of the object given to you

What is Volume? Volume the amount of space taken up by an object or substance. Volume the amount of space taken up by an object or substance.

Volume can be measured with… Ruler Ruler Graduted Cylinder or … Graduted Cylinder or …

Units for Volume Liters (L) Liters (L) Milliliters (mL) or Milliliters (mL) or Centimeters cubed (cm3) Centimeters cubed (cm3) 1 L = 1000 mL 1 mL = 1 cm 3

Measuring volume of a regular shaped object ….Like a cube Volume = 5x5x5 = 125 cm 3

Your Turn! Find the volume of your cube and record it on your handout Find the volume of your cube and record it on your handout

Measuring volume of a liquid Volume should be read from the Meniscus of a graduated cylinder

Measuring volume of an irregularly shaped object …like a fish 1.Find initial volume 2.Put object in 3.Find final volume 4.Subtract two values

Volume of water = 32 mL Volume of water + fish = 38 mL Volume of fish: 38mL – 32mL = 6 mL

Your Turn! Find the volume of your marble Find the volume of your marble

What is Density? Density is the measure of how tightly compact the matter in a substance is. Density is the measure of how tightly compact the matter in a substance is. Density = mass/volume Density = mass/volume

Example Which do you think is more dense: a Styrofoam ball or a marble? Marble

Marble: Mass = 8.1 g Volume = 2.5mL Density = 8.1g/2.5mL = 3.24 g/mL D = m/V

Styrofoam: Mass = 4.8 g Volume = 30 mL Density = 4.8g/30mL =0.16 g/mL D = m/V

Find the Density of a Penny 1.Find the mass of a group of pennies 2.Find the volume using a graduated cylinder 3.Divide the mass by the volume

DENSITY OF WATER D water = 1.00 g/mL ALWAYS!

Units for Density g/cm 3 g/cm 3 g/mL g/mL kg/m 3 kg/m 3

Independent Practice: You may work with a partner Tips for working in a group 1.Read the question to yourself first 2.Try to find the answer on your own 3.Compare it to your partner’s 4.Discuss any differences in your answers