Identifying Unknown Substances

WARM - UP Update your Table of Contents Write your homework – leave it to be stamped Get your test off the front counter to take home DateSession # ActivityPage # 9/25 & 9/26 12 Physical Vs. Chemical Warm-up & Review 21 Identifying Unknown Substances Note Guide 22

Equation Challenge: H 2 O (liquid)  H 2 O (gas) - Same substance on each side of the equation – structure or identity stayed the same - One side has liquid water, the other side has gaseous water – phase change - PHYSICAL CHANGE CH 4 + 2O 2  CO 2 + 2H 2 O - Same elements on each side of the equation – BUT structure or identity has changed - Different substances have formed on each side of the equation - CHEMICAL CHANGE

“Paper Bag Properties” In your paper bag there are several objects. Choose 1 person to stick their hand in the bag WITHOUT looking…they will have to pull out what I ask for! How did you know you had the right object? Describe its properties…

BIG QUESTION: If you have one or more unidentified substances, what could you do to start identifying them? ANSWER: Use their physical & chemical properties! Knowing the physical & chemical properties of different substances can be useful…

REMEMBER: Every single element on the Periodic Table, as well as other substances has its own set of physical and chemical properties like density, melting point, chemical reactivity etc.

Scenario 1: What Would You Do? You are thirsty and need water to survive. You have 3 containers of clear liquid…how can you start identifying what they are so you know which one is safe to drink? Which properties would be helpful?

Scenario 2: What Would You Do? You have a cup full of sand and sugar. How would you separate them? What properties would be helpful? Since you know that sugar is soluble in water and sand is not, you could add the 2 substances to a glass of water. You could pour the mixture over a filter so the sand is blocked, but the sugar water passes through. Then, allow the water to evaporate out and the sugar will be left over.

Scenario 3: What Would You Do? You work at a recycling plant and you must begin to separate the metals. What property would you use to help you? They use large magnets. Since steel has magnetic properties, the steel cans will stick to the large magnet and be dropped off in one bin, while the aluminum cans are left behind to be dumped into another bin since they do not have magnetic properties.

Scenario 4: What Would You Do? There is a deposit of silver mixed with sulfur. Silver has a density of 10.5 g/cm 3 and a melting point of 962 degrees Celsius. Sulfur has a density of 2.07 g/cm 3 and a melting point of 115 degrees Celsius. How can these physical properties be used to separate silver and sulfur? Heat the mixture until the sulfur melts. The solid silver will sink to the bottom because it is denser and can be removed leaving the liquid sulfur behind.

Quick Write: Write Everything You Can About this Substance!

Quick Write: Tell Me Everything You Can About this Substance! DID YOU HAVE… Shiny Metallic looking Flammable Gives off light when burned Silver/gray Malleable Looks sharp Reactive WHAT ELSE? Magnesium

Unknown Substances Practice Chart You have a chart with 10 UNKNOWN substances. BUT, you also have a copy of a list of KNOWN substances and some of their properties. Use the list of KNOWN substances to figure out what your UNKNOWN substances are.

Classwork/Homework Classwork/Homework: Choose one element from the Periodic Table and use your technology to find 2 physical and 2 chemical properties for that element. THEN, attempt to explain why it has those properties. DON’T chose Magnesium