Probably a Property
A characteristic used to describe or identify a substance.
property of matter
Which is a chemical change: crushing a can, melting ice, or rusting a nail?
Rusting a nail.
In 3H₂O, what does the coefficient 3 tell you?
There are three water molecules.
An ice cube melts into water. Does its mass increase, decrease, or stay the same if no water is lost?
Stay the same.
What do we call a testable explanation or prediction?
A hypothesis.
What is the difference between a physical property and a chemical property?
A physical property can be observed without changing a substance’s identity.
A chemical property describes its ability to form new substances.
A student sees bubbles in boiling water and says a chemical change occurred. Are bubbles alone enough to support that conclusion? Explain.
No. Boiling changes liquid water into water vapor; both are still water. No new substance forms.
Which has a pH below 7—an acid or a base?
acid
Can matter be created or destroyed during a chemical reaction?
No
What variable does a scientist purposely change in an experiment?
The independent variable.
Which of these is not a physical property?
Color
Density
Flammability
Magnetism
Flammability
What holds atoms in a compound together?
chemical bonds
One reaction absorbs heat from its surroundings; another releases heat. Name each type.
Absorbing heat: endothermic. Releasing heat: exothermic.
During a chemical reaction, atoms are destroyed or rearranged?
Rearranged
You test whether fertilizer affects plant growth. You measure each plant’s height. What is the dependent variable?
Plant height.
You are choosing a material for a cooking pot.--Which property of matter would you need to focus on?
Conductivity
H-
Did the hydrogen atom gain or lose an electron?
Identify each reaction as synthesis or decomposition:
A. Two substances combine to form one compound.
B. One compound breaks apart into simpler substances.
A. Synthesis. B. Decomposition.
Vinegar and baking soda react in an open cup. Afterward, the cup and its contents have less mass. Where did the “missing” matter go?
Gas formed and escaped into the air.
You give one group of plants fertilizer and another group no fertilizer. Which is the control group, and why?
The group without fertilizer; it provides a comparison.
A student says, “Flammability is a physical property because you can see a substance burning.” Explain why the student’s reasoning is incorrect.
Being visible does not make a property physical. Flammability is chemical because burning changes a substance into new substances.
One atom transfers an electron to another. The atoms become oppositely charged ions that attract each other. What type of bond forms?
An ionic bond.
A chemical reaction makes the surrounding water warmer. Is the reaction endothermic or exothermic, and how do you know?
Exothermic, because it releases heat into the surrounding water.
Fix this equation so it follows the law of conservation of mass:
H₂ + O₂ → H₂O
2H₂ + O₂ → 2H₂O
You test how water temperature affects how quickly sugar dissolves. Identify the independent variable, dependent variable, and one variable to keep constant.
Independent: water temperature. Dependent: time for sugar to dissolve. Constant: amount of sugar, amount of water, or stirring method.